1. Field of the Invention
The invention relates to a throat and cone gas injector and a gas distribution grid containing same. More particularly, the invention relates to a throat and cone gas injector and to a gas distribution grid containing a plurality of these injectors useful for injecting a gas into a slurry which contains particulate solids, with reduced solids attrition and injector plugging.
2. Background of the Invention
There are many applications in which a gas must be injected up into a slurry which comprises particulate solids in a liquid. These include coal liquefaction, resid refining, other hydrogenation processes, slurry hydrocarbon and oxygenate synthesis, waste water treating, etc. The gas is typically injected up into the slurry by means of a horizontal gas distribution grid, which is also referred to as a plate or tray, located at the bottom of the slurry in a reactor or other vessel, and over a gas space or cavity called a plenum. The tray contains a plurality of gas injectors extending therethrough for uniformly distributing the gas up into the slurry. These gas injectors can be vertical holes in the tray, bubble caps, and the like as is well known. Problems associated with these trays include solids attrition and plugging of the injectors if the gas pressure drops. While solids plugging of the gas injectors is never desirable, in some applications it is also important to avoid solids attrition. One specific example is a slurry hydrocarbon synthesis (HCS) process in which a synthesis gas (syngas) comprising a mixture of H.sub.2 and CO is bubbled up into and through a slurry in a reactor at reaction conditions effective to convert the syngas to hydrocarbons, at least a portion of which are liquid at the reaction conditions. In this process, the slurry comprises solid catalyst particles and gas bubbles in a hydrocarbon slurry liquid, with the slurry liquid comprising liquid HCS products. Reactors which contain a three phase slurry are sometimes referred to as slurry "bubble columns", as is disclosed in U.S. Pat. No. 5,348,982. The amount of syngas injected up into the slurry to provide the desired level of hydrocarbon synthesis is typically more than that needed to keep the catalyst particles dispersed in the liquid. Problems encountered with this (and other processes) include plugging of the gas injectors by the catalyst particles, catalyst particle attrition by the gas which produces fines and results in catalyst loss and plugging units downstream of the reactor, deactivation of catalyst settling on the flat spaces on the tray and catalyst falling down through the injectors into the plenum space below. It would therefore be an improvement to the art to use gas injecting means which reduce or eliminate any of these problems.